The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The miniaturization of the various components, however, presents its own set of challenges and obstacles. As higher recording densities have been adopted for magnetic recording, tunneling magnetoresistance (TMR) films and current perpendicular to plane (CPP) films have been implemented into HDD read heads. In magnetoresistance effect-type read heads such as this, a sense current flows in a direction perpendicular to a film surface, and a read output is produced in response to the magnetization orientation of the recording medium caused by changes in the film resistance and changes in the relative angle of the magnetization of the pinned layer and the magnetization of the free layer of a magnetoresistance effect film, which have their origin in the stray magnetic field from the recording medium. In order to ensure linearity of the read output at this time, a hard magnetic film is typically arranged at a left and right in a cross-track direction from the magnetoresistance effect film to act as a domain controlling layer with respect to the magnetization free layer. In addition, in order to increase the read-write resolution in a bit direction, a soft magnetic shield layer is arranged above and below the magnetoresistance effect film and the hard magnetic film.
In the above described magnetoresistance effect-type read head, a width in a film surface direction (hereinafter track-width direction) of the magnetic free layer of the magnetoresistance effect film exposed to the ABS of the head and the distance between the top and bottom soft magnetic shield layers (hereinafter gap length) must be set to appropriate widths corresponding to the surface recording density of the HDD recording medium. In addition, in order to suppress changes in the magnetic domain controlling characteristics, the height length, which expresses the length of the magnetoresistance effect film in the back-side direction of the film surface (hereinafter height direction) as seen from the ABS, must also be set to an appropriate width.
Increased recording densities in HDDs have necessitated a significant reduction in the recording bit size of the media thereof. In turn, this has necessitated a reduction in the track width and gap length of the read head. However, processes for fabricating a read head with very narrow track width may result in resolution limitations during the patterning performed by the exposure device, as well as variations in the process dimensions.
The height length of the read head is also typically reduced, similar to the reduction in track width and gap length. A significantly reduced height length, however, may affect the final finishing shape, in the height direction, of the read head and may significantly impact the read characteristics of the head. For example, if undulations are formed in the back edge (in the height direction) of the read head as a result of processing, undulations may also be produced in the soft magnetic shield layer fabricated thereon. Furthermore, these undulations may also be generated in the magnetic domain structure of the shield, resulting in deterioration in the shield performance. Moreover, for convex undulations (e.g., convexities) in particular, the distance between the magnetization free layer edge portion of the magnetoresistance effect film and the soft magnetic shield at the height back edge may be increased, which may adversely affect the function of the soft magnetic shield as a flux guide, resulting in a drop in the output during reproduction.
In conventional HDDs, the shape of the height edge portion of the read head is generally established by the employment of a conventional lift-off process. This conventional lift-off process typically employs a two layer resist as a mask material, where the underlayer resist section is undercut. However, an insulating material used for backfilling in this conventional process tends to bulge at various portions of the magnetoresistance film edge during the deposition thereof (see, e.g., FIG. 5). Consequently, the bulging of the insulating material results in a loss of planarity. Even where a polishing step is implemented to remove existing fences, the convexity of the insulating material defined by the fences typically remains after a stopper film is removed.